Redondavenator
Encyclopedia
Redondavenator is a genus
of sphenosuchia
n, a type of basal
crocodylomorph
, the clade
that comprises the crocodilia
ns and their closest kin. It is known from a partial upper jaw and left shoulder girdle found in rocks of the Norian
-Rhaetian
-age Upper Triassic Redonda Formation, northeastern New Mexico
. It is notable for its large size; the minimum estimated skull length for the holotype
individual is 60 centimetres (23.6 in).
NMMNH
P–125615, a partial anterior skull and associated partial left scapula
and coracoid. These fossils were collected during one of the New Mexico Museum of Natural History and Science
expeditions to the Redonda Formation of Quay County
, New Mexico in the 1980s and 1990s. A partial lower jaw was once thought to belong as well, but was found to have come from a phytosaur
. The fossils were found in a conglomerate
layer high in the formation, above lacustrine
shale
s with fossils of semionotid
fish. The conglomerate is interpreted as debris flow
s along a lake margin.
Redondavenator was named in 2005 by Sterling Nesbitt and colleagues. The type species
is R. quayensis, referring to Quay County. The preserved portion of the skull includes the premaxilla
e (snout tip) and parts of the maxilla
e (main tooth-bearing bones of the upper jaw) and nasals
, in front of the antorbital fenestra
. The fourth and fifth teeth of the maxilla
were enlarged. Ridges and other sculpting were present on the upper surface of the snout. The shoulder bones were robust. Nesbitt and colleagues described their new genus as a basal sphenosuchian. They interpreted it as filling a large terrestrial predator role that had been left empty by the extinction of rauisuchia
ns.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of sphenosuchia
Sphenosuchia
Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Late Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms, which include all living crocodilians.-Stratigraphic...
n, a type of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
crocodylomorph
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
, the clade
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
that comprises the crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns and their closest kin. It is known from a partial upper jaw and left shoulder girdle found in rocks of the Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
-Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...
-age Upper Triassic Redonda Formation, northeastern New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. It is notable for its large size; the minimum estimated skull length for the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
individual is 60 centimetres (23.6 in).
History and description
Redondavenator is based onHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
NMMNH
New Mexico Museum of Natural History and Science
The New Mexico Museum of Natural History and Science is a natural history and science museum in Albuquerque, New Mexico near Old Town Albuquerque. The Museum was founded in 1986....
P–125615, a partial anterior skull and associated partial left scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
and coracoid. These fossils were collected during one of the New Mexico Museum of Natural History and Science
New Mexico Museum of Natural History and Science
The New Mexico Museum of Natural History and Science is a natural history and science museum in Albuquerque, New Mexico near Old Town Albuquerque. The Museum was founded in 1986....
expeditions to the Redonda Formation of Quay County
Quay County, New Mexico
-2010:Whereas according to the 2010 U.S. Census Bureau:*86.1% White*1.1% Black*1.2% Native American*1.0% Asian*0.0% Native Hawaiian or Pacific Islander*3.4% Two or more races*7.2% Other races*42.4% Hispanic or Latino -2000:...
, New Mexico in the 1980s and 1990s. A partial lower jaw was once thought to belong as well, but was found to have come from a phytosaur
Phytosaur
Phytosaurs are an extinct group of large semi-aquatic Late Triassic archosaurs. Phytosaurs belong to the family Phytosauridae and the order Phytosauria. They were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodiles in size, appearance, and lifestyle, an example...
. The fossils were found in a conglomerate
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
layer high in the formation, above lacustrine
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s with fossils of semionotid
Semionotus
Semionotus is an extinct genus of ray-finned fish found throughout Northern Pangaea during the late Triassic, becoming extinct at the start of the Jurassic.-External links:...
fish. The conglomerate is interpreted as debris flow
Debris flow
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. It is differentiated from a mudflow in terms of the viscosity and textural properties of the flow. Flows can carry material ranging in size from clay to boulders, and may...
s along a lake margin.
Redondavenator was named in 2005 by Sterling Nesbitt and colleagues. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is R. quayensis, referring to Quay County. The preserved portion of the skull includes the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
e (snout tip) and parts of the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e (main tooth-bearing bones of the upper jaw) and nasals
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
, in front of the antorbital fenestra
Antorbital fenestra
An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...
. The fourth and fifth teeth of the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
were enlarged. Ridges and other sculpting were present on the upper surface of the snout. The shoulder bones were robust. Nesbitt and colleagues described their new genus as a basal sphenosuchian. They interpreted it as filling a large terrestrial predator role that had been left empty by the extinction of rauisuchia
Rauisuchia
Rauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
ns.